Transition metal complexes of various types are important components of olefin P/O catalysts. These catalysts are typically used in a variety of physical forms, for instance in solution, as a suspension, or supported on another solid material, and these forms may be used in one or more types of P/O processes, such as solution, suspension or gas phase processes.
One type of olefin P/O catalyst utilizes a transition metal, often an iron or cobalt, complex of a 2,6-diacylpyridine(bisimine) or a 2,6-pyridinedicarboxaldehyde(bisimine). This type of catalyst is particularly useful in polymerizing ethylene to form high density polyethylene (HDPE), or oligomerizing ethylene to linear α-olefins (LAOs), see for instance U.S. Pat. Nos. 5,955,555, 6,103,946, 6,534,691, and 6,710,006, and World patent applications 99/92981, 00/50470, and 03/0119921, all of which are hereby included by reference. These types of catalysts are also useful for cooligomerizing ethylene and other α-olefins, see for instance WO 02/28805, which is hereby included by reference. In such processes these complexes are sometimes added directly to the P/O process (or first an initial step wherein these complexes are converted to active catalysts) as suspensions in inert liquids. Suspensions prepared from these complexes in the solid form obtained from the synthesis of the complex by simple agitation in an inert liquid yields suspensions, which settle rapidly. Grinding of the solid complexes is complicated by the fact that they are somewhat air, moisture and heat sensitive. Thus, methods of preparing (improved) suspensions of these complexes are useful.
It is known that sonicating (treating with ultrasonic energy) solid particulate material in liquid suspension can deagglomerate and in some instances reduce the primary particle size of solids. However, sonication under these circumstances can lead to localized heating, and in some instances will not reduce particle sizes.
U.S. Pat. Nos. 5,559,199, 5,650,471 and 6,143,827 describe examples in which a mixture of a metallocene polymerization catalyst, and inert liquid and an alkylaluminum compound are treated with ultrasound to obtain a catalyst solution. Nothing is stated about obtaining a suspension of a catalyst.
U.S. Pat. No. 6,562,918 describes a process for producing an improved supported catalyst by exposing certain catalyst components to ultrasound. Unsupported catalysts and their suspensions are not mentioned.